Dopamine receptors are one kind of G protein-coupled receptors that are present in the central nerve system. The dopamine receptors are classified into the dopamine D1 receptor-like family and the dopamine D2 receptor-like family. Dopamine D1 and D5 receptors in the dopamine receptors belong to the dopamine D1 receptor-like family. Further, dopamine D2, D3 and D4 receptors belong to the dopamine D2 receptor-like family.
It has been reported that the dopamine D1 receptor is coupled with Gas which is a promoting G protein, thereby activating an adenylate cyclase and increasing the production of intracelluar cAMP to promote the activity of a protein kinase A and exert various functions (Medicinal Research Reviews, 2009, 29(2), p. 272-294).
There is a report suggesting that in patients with schizophrenia, dopamine D1 receptors are significantly decreased in a part of the frontal lobe called the prefrontal cortex and that the degree of decrease in the dopamine D1 receptors is correlated with the intensity of negative symptoms of schizophrenia or the performance of the Wisconsin Card Sorting Test which is a test on functions of the frontal lobe, and as a result, the decrease in dopamine D1 receptors in the prefrontal cortex plays an important role in cognitive impairment or negative symptoms of schizophrenia (Nature, 1997, Feb. 13, 385(6617), p. 634-636).
There are reports suggesting that dopamine D1 receptor agonists are useful in cognitive impairment models (European Neuropsychopharmcology, 2009, 19(6), p. 440-450; Psychopharmacology, 2010, 210(3), p. 407-418; Molecular Pharmacology, 2007, 71(6), p. 1598-1609).
There are also reports suggesting that dopamine D1 receptors are involved in negative symptoms of schizophrenia (The American Journal of Psychiatry, 2002, 159(5), p. 761-767; Pharmacopsychiatry, 2006, 39(3), p. 115-116).
Accordingly, the dopamine D1 receptor agonists are expected as an agent for ameliorating cognitive impairment or negative symptoms of schizophrenia by stimulating the dopamine D1 receptors in the prefrontal cortex.
There are also reports suggesting the possibility of applying dopamine D1 receptor agonists to Parkinson's disease (Current Opinion in Investigational Drugs, 2001, 2(11), p. 1582-1591) or Alzheimer's disease (The Journal of Biological Chemistry, 2011, 286(5), p. 3270-3276).
Furthermore, there are reports that dopamine D1 receptor agonists exhibit effectiveness with the respective animal models with Huntington's disease (Neurodegenerative Diseases, 2011, 8(4), p. 230-239) or drug addictions (Neuroscience Letters, 2012, 513(2), p. 214-218).
Furthermore, there is also a suggestion of the possibility of applying dopamine D1 receptor agonists to cognitive impairment in attention deficit hyperactivity disorder (ADHD) (Neuropsychologia, 2013, 51(2), p. 235-266).
Accordingly, compounds stimulating the dopamine D1 receptors are considered to be promising as a drug for preventing and/or treating diseases such as cognitive impairment, negative symptoms of schizophrenia, Parkinson's disease, Alzheimer's disease, Huntington's disease, drug addictions, or the like.
There are cases where dopamine D1 receptor agonists are also used as a peripheral antihypertensive (The New England Journal of Medicine, 2001, 345(21), p. 1548). On the other hand, for example, there is a report that dihydrexidine which is a dopamine D1 receptor agonist has side effects affecting blood pressure (Clinical Neuropharmacology, 1998, 21(6), p. 339-343).
G Protein-coupled receptors have been studied as an important target for drug discovery for a long period of time. In recent years, it has been found that many G protein-coupled receptors have allosteric sites other than orthosteric ligand sites (ACS Chemical Biology, 2008, 3(9), p. 530-541). Accordingly, drug discovery which targets an allosteric site in a G protein-coupled receptor as a drug discovery target has been actively studied (British Journal of Pharmacology, 2012, 165(6), p. 1659-1669).
A positive allosteric modulator (hereinafter referred to as PAM in some cases) is a compound which binds to a site other than a site to which an endogenous ligand binds with respect to a receptor, thereby enhancing the receptor function. PAM does not increase the receptor function in itself, but increases the receptor function in the presence of a ligand.
Therefore, a dopamine D1 receptor PAM (hereinafter referred to as D1 PAM in some cases) has a dopamine D1 receptor positive allosteric modulating activity, can be used for preventing and/or treating cognitive impairment, negative symptoms of schizophrenia, Parkinson's disease, Alzheimer's disease, Huntington's disease, drug addictions, and the like, and is expected to be useful as a drug having fewer side effects, as compared with dopamine D1 receptor agonists.
In Patent Document 1, it is reported that a compound of the formula (A) has benzodiazepine ω3 receptor agonistic action. In Claims, anti-anxiety or anti-depressant is described. However, there is no specific disclosure of the compound of the present invention.

(in which R1 and R2 each independently represent H, an alkyl group which may be substituted, or the like. X represents O, S, NR10, or CR11R12. Refer to this publication for the other symbols.)
In Patent Document 2, it is reported that a compound of the formula (B) exhibits a urotensin II agonistic and inhibitory action, and is useful in congestive heart failure or the like.

(Refer to this publication for the symbols in the formula.)
In Patent Document 3, it is reported that a compound of the formula (C) exhibits a cannabinoid 1 agonistic and/or inverse agonistic action, and is useful as a central functional agent or the like.

(in which R1 and R2 are each alkyl, cycloalkyl, aryl, aryl-alkyl, heteroaryl, heteroaryl-alkyl, or the like. Refer to this publication for the other symbols.)
In Patent Document 4, it is reported that a compound of the formula (D) is useful for treating and/or preventing movement disorder and/or movement fluctuations.

(in which R3 and R3a are each H or unsubstituted C1-4 alkyl. Refer to this publication for the other symbols.)
In Patent Document 5, it is reported that a compound of the formula (E) is useful for treating and/or preventing anxiety, depression, cognitive impairment, or the like as a GABAA modulator.

(in which A, B, C, and D represent N or CH. X is a bond, CH2, or CHCH. R1 is Ph, C1-6 alkyl, or the like. Refer to this publication for the other symbols.)